MSM are a key risk group in the United States and are disproportionately impacted in terms of HIV prevalence and incidence. For decades, black/white disparities in HIV prevalence and incidence have been recognized. Much of the dialogue about disparities has focused on what might cause disparities in new HIV infections, and we recently completed an NIMH-supported R01 (InvolveMENt) to examine reasons for black/white HIV disparities in an HIV/STI incidence cohort of black and white MSM in Atlanta. An early, important finding from that study is that HIV-negative black MSM, while having comparable levels of individual risk behaviors, have a much greater chance of having a sex partner with a detectable HIV viral load - thus black MSM are at higher risk for acquiring HIV, despite comparable individual risk behaviors. But disparities extend beyond risks for infection: black MSM may fare less well in the treatment cascade because of later access to care, lower adherence to antiretroviral therapy (ARV), mistrust of providers, or, perhaps, stigma and discrimination. Recent national estimates have documented consistent racial disparities at each step of the HIV treatment cascade, culminating in a 30% lower likelihood of viral suppression among black non-Hispanic, compared to white non- Hispanic HIV-positive individuals. This pattern has been observed in the state of Georgia. In a Lancet systematic review in 2012, Millet et al. illustrated that the racial disparities after HIV infection are profound for MSM: black MSM were found to be less likely to initiate ARVT, less likely to adhere to therapy, and less likely to be virally suppressed. Further, this analysis suggested that structural factors, such as education, poverty, and lack of employment, played key roles in care disparities. Thus, we propose to build on our previous MSM cohort in Atlanta, to identify the factors that are prospectively associated with racial disparities in effective HIV care and prevention. The proposed work will build on the infrastructure, community relationships, multilevel conceptual framework and multidisciplinary team assembled for our previous grant, but will shift focus from HIV-negative MSM to those living with HIV. The design will be a prospective cohort of HIV-positive black and white MSM in Atlanta, with rich laboratory, survey, and qualitative data collections. Results will help provide deeper understanding of why disparities in care outcomes occur, and will provide actionable data for the development of interventions to reduce disparities in effective HIV care.